2. Proton beam therapy is an advanced form of
radiation therapy used by radiation oncologists to
treat cancerous and some non-cancerous tumours.
It uses high-powered energy particles known as
protons instead of X-rays to directly deliver
radiation to the tumours.
INTRODUCTION
3.
4. o Idea of using protons in medical treatment was
first suggested in 1946 by physicist Robert
R. Wilson, Ph. D.
First attempts to use proton radiation to treat
patients began in the 1950s in nuclear physics
research facilities,but applications were limited.
HISTORY
5. o In the late 1970s, imaging advancements
coupled with the development of sophisticated
computers and improved accelerator and
treatment delivery technology made proton
therapy more viable for routine medical
applications
6. PROTON INTERACTION
It interacts with electrons and atomic nuclei in medium through
Coulomb force
i. Inelastic collision.
ii. Elastic scattering.
7. PRODUCTION OF PROTONS
Protons are extracted from hydrogen atoms and
accelerated to almost the speed of light using a
cyclotron. Electromagnets focus and bend the
protons down a beamline to a treatment room.
Cyclotron accelerates the particle between 2
semicircular cavities and is smaller in size.
9. PARTS OF PROTON UNIT
• SCANNING
PROTON BEAM
PORT.
• GANTRY
• 2 SETS OF FPD’S
• X-RAY SOURCE
• X-RAY TUBE
• ROBOTIC COUCH
FPD-FLAT PANNEL DETECTORS
10. Procedure during Pbt Treatment
• Placed on a treatment table during simulation to determine
position .Immobalization devices such as molds and casts are
used to restruct movements.
• The radiation oncologist will position the gantry so the proton
beam is lined up with the marks on your skin indicating the
location of the tumor.
• An X-ray or another imaging scan will be taken to confirm that
you are in the right position and everything is aligned.
• Once the machine is on, the particle accelerator in a
separate room speeds up protons and sends them to the
gantry in the treatment room. The gantry focuses protons into
11. a thin beam and aims them at the tumor. The gantry might move
around your body to treat the tumor from different angles.
• The treatment usually takes 15-30 minutes.
12. DIFFERENCE BETWEEN PROTON AND
PHOTON.
• proton therapy delivers a beam of
proton particles that stops at the
tumor, so it’s less likely to damage
nearby healthy tissues.
• More expensive.
• Less side effects.
• Traditional radiation delivers x-
rays, or beams of photons, to the
tumor and beyond it. This can
damage nearby healthy tissues
and can cause significant side
effect.
• Less expensive.
• More side effects.
15. PARTICLE ACCELERATORS
Protons can be accelerated to high energies using:-
• A linear accelerator.
• A cyclotron.
• A syncrotron.
• High gradient Electrostatic Accelerator.
• Laser Plasma particle Accelerator.
Cyclotrons and syncrotrons are currently the main
accelerators for proton therapy.
High gradient electrostatic accelerators and Laser plasma
particle accelerators are on the horizon.
16. CYCLOTRONS
• Two short metallic cylinder, called DEES.
• Placed between poles of direct magnetic field.
• An alternating potential is applied between Dees.
• Frequency is adjusted of alternating potential to
accelerate the particle as it passes from one Dee to
another.
• With each pass,the energy of the particle and the
radius of the orbit increase.
17. • Cyclotron was introduced in 1929 by Ernest
Lawrence.
• A fixed energy machine which produces
continuous beam of monoenergetic (250Mev)
photons.
• This energy is sufficient to treat tumors at any
depth by modulating the range and intensity of
beam which energy degrades.
• Cyclotrons can produce a large photon beam
current of up to 300nA and thus deliver proton
therapy at high dose rate.
CYCLOTRONS (contd)
18.
19. Disadvantages ofCyclotron.
• Inability to change the energy of extracted
particles directly.
• Energy degradation by material in the beam path
leads to an increase in energy spread and beam
emittance and reduces the efficiency of the
system.
• More shielding is required because of secondary
radiation.
20. SYNCROTRON
• They produce the
proton beam.
• It is modified
Cyclotrons.
• Syncrotron provides
energy variation by
extracting the
protons when they
have reached their
desired energy.
21.
22. PROTON DOSE DISTRIBUTION
• Depends on the concept of Linear Energy Transfer(LET).
• LET is defines as dE/dx, where dE is the main energy deposited
over a distance dx in media.
• The rate of energy loss due to ionization and excitation caused by
a charged particle travelling in a medium is proportional to the
square of the particle charge and inversely proportional to the
square of its velocity.
• As the particle velocity approaches 0 near the end of its range,the
rate of energy loss becomes maximum.
• The sharp increase or peak in dose deposition at the end of
particle range is called the Bragg peak.
23. BEAM DELIVERY SYSTEM
• Proton beam exiting the transport system is a pencil-
shaped beam with minimal energy and direction spread.
• Narrow Bragg peak ,not suitable for practical size tumors.
Pencil beam is either modified by:-
1. Scattering beam technique.
2. Scanning beam technique.
24. SCATTERING BEAM TECHNIQUE
• Small field: single scattering foil(made of lead)
• Larger field sizes: double scattering foil to ensure a uniform,
flat lateral dose profile.
• Modulator wheel: variable thickness absorbers in circular
rotating tracks that results in a temporal variation of the beam
energy.
• Aims to produce a dose distribution with a flat lateral profile.
• Range modulation wheels consisting of variable thickness of
acrylic glass are traditionally used for this purpose.
• Width and thickness of modulation wheels are caliberated to
achieve SOBP.
• The width of SOBP is controlled by turning the beam off when
a prescribed width is reached.
25. SCANNING BEAM TECHNIQUE
• An alternate to the use of a broad beam is to generate a narrow
mono-energetic “pencil beam” and to scan it magnetically across
the target.
• Typically the beam is scanned in zig-zag pattern in the x-y plane
perpendicular to the beam direction.
• As the pencil beam exits the transport system, it is magnetically
steered in the lateral directions to deliver dose to a large
treatment field.
• The proton beam intensity may be modulated as the beam is
moved across the field resulting in modulated scanning beam
technique or IMPT.
26. ADVANTAGES
• In contrast to broad beam technique, arbitrary shapes of uniform
high dose regions can be achieved with a single beam.
• No first and second scatters, less nuclear interactions and
therefore the neutron contamination is smaller.
• Great flexibility, which can be fully utilized in intensity-modulated
proton therapy(IMPT).
27. IMMOBILIZATON.
Immobilization devices play a major role in proton
treatment.Immobilization devices are used to immobilize the patient
during the treatment.This helps in reducing the dose to normal
tissues and maximum dose to the target.
Various immobilization devices are used in proton treatments such
as moulds, aquaplast, foam headrest, head frame etc.
Conditions for immobilization devices in proton therapy:-
• uniform, low-density if possible, material.
• devices with gradual slope and no sharp edge
• devices producing minimal imaging artifacts
• avoiding the field passing part of the frame and/or table edge
during treatment planning.
28. One Proton Couch Top
One Proton Couch Top is
rigid, lightweight and
specifically designed for
use with a robotic couch,
which is frequently used
in proton therapy
applications. The couch
top provides a wide
range of positioning and
immobilization options for
treating tumors of varying
complexities.
29. BASE OF SKULL(BoS) HEADFRAME.
The Base of Skull (BoS)
headframe is specifically
designed to meet the unique
requirements of proton therapy
for patient immobilization and
beam transmission. The BoS
headframe is engineered to
rigidly support the patient
without using a flat base that
blocks the use of important
proton beam angles.
The conformal shape is desired
to minimize the distance
between the patient and the
field defining aperture,
optimizing the beam proton
penumbra.
33. The degree of accuracy and reliability required in proton therapy
can only be guaranteed if a comprehensive quality assurance
(QA) programme is established.
QUALITY ASSURANCE is mainly divided:-
DAILY
MONTHLY
ANNUALLY
34. DAILY QA :-
• Dosimetric beam quality constancy.
• Functionality of imaging and patient
positioning systems
• Communication between different
computer systems associated with
treatment.
• Functionality of critical safety interlocks.
• Laser allignment.
35. • Couch isocentricity is checked once in a week
during the morning QA by Physics Assistants.
• Two physics assistants perform the morning
machine QA.
• A staff physicist is present on site as the
supervisor.
• Daily QA report is reviewed by a staff physicist
once in a week.
DAILY(CONTD)
36. MONTHLY QA :-
• Constancy of radiation field Dose / MU, Distal
range, SOBP width and flatness and symmetry
at one gantry angle.
• Range uniformity check
• Constancy of Output vs gantry angle.
• Gantry mechanical isocentricity check.
• Table translational motion accuracy and
mechanical isocentricity checks.
• Snout horizontal motion accuracy check.
37. • Patient positioning system accuracy check.
• X-rays and proton field coincidence check.
• Done by Physicists, Proton Physics fellows, Residents
and Physics Assistants, 12 to 16 Hours for each passive
scattering gantry.
MONTHLY(CONTD)
38.
39. ANNUAL QA:- It is divided into 3:-
• Dosimetry check.
• Mechanical check.
• Safety check.
1. DOSIMETRY CHECK :
Dose monitor system calibration.
Standard calibration: IAEA TRS-398 protocol with PTW 30013
Cylindrical Chamber.
Reproducibility, linearity, end effect.
Beam data constancy checks.
SOBP (PDD): Distal range, SOBP width, longitudinal
penumbra width, Spot width.
baseline constancy checks
40. 2. MECHANICAL CHECK :
COUCH
Translational and rotational movements.
Vertical axis trueness and sagging Gantry.
GANTRY
Rotational,Mechanical, X-ray system, Proton beam
isocentricity and coincidence.
Gantry angle indicator.
OTHER CHECKS
RMW mechanical integrity
Aperture compensator holder integrity
Hand pendant functionality
ANNUAL(CONTD)
41. X-ray system
kVp, HVL and Timer accuracies.
Exposure reproducibility.
mA Linearity.
Output constancy.
Image quality (High and low contrast resolution).
Safety.
3. SAFETY CHECK :
Door interlocks, crash buttons, radiation monitors.
Monitor unit and radiation time indicators.
Beam pause and abort buttons.
Radiation status indicator lights
Audio visual patient monitors.
Snout: Extension verification ANNUAL(CONTD)
42. PATIENT SPECIFIC QA (PASSIVE
SCATTERING FIELDS)
• MU verification measurement- 10 minutes per field + 15
minutes setup time.
o Tolerance: 3% difference from calculation.
o Outside tolerance: Use measured value.
• Aperture and compensator QA-10 minutes per field
(apertures must match with plan, compensator thickness
tolerance < 0.5 mm).
o Outside tolerance: Re-fabricate.
• Occasional 2-D dose verification for small fields.
43. PATIENT SPECIFIC QA (SPOT SCANNED
BEAM)
• Point dose measurement in “Fish Bowl” phantom for prostate
treatment fields or in Plastic Water (PW) with a IC or MatriXX
for others.
• Depth dose measurement using MatriXX in solid phantoms
• 2-D dose verification at 3 to 5 different depths for each field
with MatriXX in PW.
• 10 minutes of room time for each depth + 30 minutes of setup
and warm up time for measurement.
• Pre-measurement Preparation, Post-measurement data
analysis and report preparation and check: 4 hours for each
patient
44. PATIENT SPECIFIC QA (SCANNING BEAM)
• QA tolerance
Point doses: Within 2% or 2 mm of calculation.
2-D dose distribution: 90% of the pixels have the passing
gamma with 2% dose or 2 mm distance agreement criteria.
• Actions if QA result exceeds tolerance.
Understand the source of disagreement and rectify any
measurement and planning issues
46. ADVANTAGES OF PROTON BEAM THERAPY
• Minimises radiation exposure of healthy tissues.
• Fewer short and long-term effects.
• Lower integral dose per treatment.
• Can treat recurrent tumors in patients who have already received
radiation.
• Potentially reduces the risk of secondary cancers.
• Improve patient's quality of life.
47. RISKS AND SIDE EFFECTS
Generally the side effects are less compared to photon beam
therapy. But some side effects are:-
• Fatigue
• Hair loss
• Skin redness
• Soreness around the body part being treated
NOTE:-Patients who are PREGNANT and Have
Systemic Lupus Erythematosus, Scleroderma, and
other connective tissue disorders are not advised for
treatment.
48. CONCLUSION
PBT is an advanced radiation treatment that represents an alternative
to photon therapy for the treatment of cancer. Proton therapy uses the
positively charged particles in an atom (protons) that release their
energy within the target: the tumor. There is lower entrance radiation
and virtually none travels beyond the tumor.
PROTON CENTRES IN INDIA
• APPOLO PROTON CANCER CENTER,CHENNAI
• ACTREC,MUMBAI
